In recent years, a medical device that examines the inside of a body using a capsule endoscope capable of being self-propelled through the inside of the body is known. The capsule endoscope in this medical device generally imposes less burden on a subject because, unlike conventional endoscopes, it does not require a tube that passes through the gullet or the like for operating the endoscope. When a subject swallows the capsule endoscope, the capsule endoscope moves through the inside of the body according to a peristaltic movement of the stomach or the intestines while capturing images of the surroundings with an internal camera, and the captured images are transmitted to a capsule controller that controls the self-propulsion of the capsule endoscope from the outside of the body and are stored in a storage medium. Thereafter, the capsule endoscope is discharged outside from the anus.
Such a self-propelled capsule endoscope can move to a destination to be examined by itself as well as moving passively according to the peristaltic movement. For example, Patent Document 1 discloses a capsule endoscope in which a magnet having a magnetization direction in a direction orthogonal to an axial direction (longitudinal direction) is mounted and a propulsive power generating portion having a spiral structure is provided at the rear end in the axial direction. This capsule endoscope is configured such that the magnet rotates in response to a rotational magnetic field generated by a capsule controller disposed at the outside of the body, and the propulsive power generating portion rotates with rotation of the magnet, whereby propulsive power in the axial direction is generated.
Patent Document 2 discloses a capsule endoscope in which a magnet having a magnetization direction in an axial direction (longitudinal direction) is mounted and a fin portion is provided at the rear end in the axial direction. This capsule endoscope is configured such that the magnet vibrates in response to an alternating magnetic field generated by a capsule controller disposed at the outside, and the fin portion vibrates by bending with the vibration of the magnet to push surrounding liquid backward, whereby propulsive power in the axial direction is generated. In Patent Document 2, the position of an electromagnet that generates a one-directional alternating magnetic field is controlled by a guide rail and a lift so that the capsule endoscope is moved to a destination to be examined.
Since the attitude of the capsule endoscope of Patent Document 2 is stable so that the fin portion bends in the direction of the alternating magnetic field, the capsule endoscope can obtain stable images and perform examinations easily as compared to the capsule endoscope of Patent Document 1 in which images captured by the internal camera are likely to rotate or be inclined unstably with rotation of the propulsive power generating portion. Moreover, since the capsule endoscope of Patent Document 2 can move a large amount of liquid backward with strong force by means of the fin portion, it is possible to easily increase the propulsive power with a small size as compared to the capsule endoscope of Patent Document 1 in which the propulsive power is obtained by rotation of the propulsive power generating portion, and to reduce the possibility that the body walls (wall surfaces inside the body) are damaged with friction.